Memory devices are typically provided as internal, semiconductor, integrated circuit devices in computers or other electronic devices. There are many different types of memory including random-access memory (RAM), read only memory (ROM), dynamic random access memory (DRAM), synchronous dynamic random access memory (SDRAM), and flash memory.
Flash memory devices have developed into a popular source of non-volatile memory for a wide range of electronic applications. Flash memory devices typically use a one-transistor memory cell that allows for high memory densities, high reliability, and low power consumption. Changes in threshold voltage of the memory cells, through programming (which is often referred to as writing) of charge storage structures (e.g., floating gates or charge traps) or other physical phenomena (e.g., phase change or polarization), determine the data value of each cell. Common uses for flash memory include personal computers, personal digital assistants (PDAs), digital cameras, digital media players, cellular telephones, solid state drives and removable memory modules, and the uses are growing.
Integrated circuit devices generally are powered by two or more externally-supplied voltages, such as Vcc and Vss. In addition to the supply voltages, integrated circuit devices often generate other voltages utilized in the operation of that device. For example, in a memory device, such internally-generated voltages are often utilized during access operations, such as during a read operation, a program operation (often referred to as a write operation), or an erase operation. The internally-generated voltages are often higher or lower than any supply voltage.
Generating other voltage levels from a supply voltage is often performed using a charge pump or other voltage generation circuit. Charge pumps often utilize alternating switched capacitances (e.g., capacitors) to generate a higher or lower voltage from a supply voltage. Power efficiency is often an important consideration in the design and usage of integrated circuit devices, and the generation and transmission of these internal voltages often results in significant power losses.
For the reasons stated above, and for other reasons stated below which will become apparent to those skilled in the art upon reading and understanding the present specification, there is a need in the art for alternative methods of generating and transmitting voltages, and apparatus to perform such methods.